The present invention relates to latch assemblies, and in particular latch assemblies which are manually operable alone or latch assemblies which are both manually operable and power actuator operable.
The present invention is particularly applicable to latches used on vehicle doors such as car passenger doors or car trunk doors.
Vehicle door latches are known which are released using a power actuator. Typically the door latch would have a latch bolt retained in position by a pawl and the actuator would act on a release lever connected to the pawl or would act directly on the pawl to release the latch. After the actuator""s power stroke, the actuator must return to its initial state in one of three traditional methods:
a) Reverse energizing of the motor such that the motor is spun in its opposite direction e.g., reversing the polarity on an electric motor,
b) Declutching a clutch mechanism situated between the motor and a drive train of the actuating mechanism and returning the drive train by a weak spring,
c) Back driving the whole of the actuator mechanism including motor and drive train a strong spring.
The problem with reversing the polarity is that many modern vehicle controllers do not allow reverse polarity and more noise is generated due to longer motor operating duration.
The problem with an actuator incorporating a clutch mechanism is that the clutch mechanism itself is expensive, complex and has several parts and that such clutches do not operate consistently.
The problem with back driving the motor and power train is that the motor must be more powerful (and thus more expensive and heavier) to overcome the strong spring, more noise is generated due to longer operating duration, and some systems using helical gears cannot be back driven due to the large lead angle of the helical gears.
Known latch assemblies have primary latched positions wherein the associated door is fully closed and secondary latched positions wherein the associated door is not fully shut but nevertheless is prevented from opening. Such an arrangement has been used particularly on passenger doors of cars as a safety feature and in a legal requirement in many countries. Typically the door seals situated around the periphery of the door, which provide a weather tight seal between the door and its associated aperture, are resilient and are compressed when the door is in its closed condition. Releasing of the latch then allows the seals to partially open the door, at least past the secondary latched position, allowing the user to then fully open the door.
However a problem with such an arrangement is that under some conditions the seal force which tends to open the door can be insufficient to push the latch bolt past the secondary latched position resulting in a door that only opens to the secondary latched position. Under such circumstances the latch has to be unlatched again from the secondary latched position either manually by pulling on a door handle again or in the case of an actuator driven latch by operating the actuator for a second time and pulling the door open. Insufficient seal load could be caused by a door frozen into a closed position, poor fit/misalignment of the door, heavy vertically opening rear trunk lids.
It is an object of the present invention to provide a latch assembly including a power actuator which does not require to be driven in a reverse direction.
It is another object of the present invention to provide a latch assembly including a power actuator which does not require clutch mechanisms between a motor and a drive train of the power actuator.
It is another object of the present invention to provide a latch assembly including a power actuator which does not require back driving of the drive train and motor.
It is another object of the present invention to provide a latch assembly having a latch mechanism that does not engage a secondary latch position when operated.
Thus according to the present invention there is provided a latching mechanism including a latch bolt moveable between a primary latched position and an open position,
a first pawl moveable between a first engaged position where it secures the latch bolt in at least its primary latched position and a second released position where it releases the latch bolt from at least its first primary latched position,
release means moveable between a first engaged position where it allows the first pawl to achieve its first engaged position and a second released position where it retains the first pawl in its second released position, and
a second pawl moveable between a first engaged position where it is capable of retaining the release means in its second released position and a second released position where it releases the release means from its second released position
such that the latch mechanism can be latched and unlatched.
According to a further aspect of the present invention there is provided latch mechanism including a power actuator, the power actuator having a motor and a drive train, the drive train having at least one abutment for engagement with a release means of the latch mechanism, energization of the motor causing the abutment to move the release means from a first engaged position to a second released position to release the latch, in which a retention means (58) is capable of retaining the release means in its second released position.
According to a further aspect of the present invention there is provided a latch mechanism including a power actuator, the power actuator having a motor and a drive train, the drive train having the plurality of abutments for engagement with a release arrangement of the latch mechanism, energization of the motor causing one of the plurality of abutments to move the release arrangement from a first engaged position to second released position to release the latch, resulting in another of the plurality of abutments co-operating with the release arrangement to provide a drive train stop.